In a communication system, covering a wide geographical area is accomplished by the use of repeaters scattered according to the prevailing terrains. The repeaters are basically used to extend the range of transmission to and from the radios operating in such a communication system. The repeaters transmit information signals constantly so as to inform their respective radios of their identification. These signals are received by the radios where their strength is evaluated and based on this strength the radios determine if they are about or have already left the zone of a specific repeater. Upon weakening of the received signal strength of the information signal the radio scans the airwaves for another strong information signal in search of a new repeater. Upon a successful scan the radio shifts to the new frequency and accesses the new repeater. Since the probability of a large number of radios simultaneously moving out of one zone to another is very low, channel collision will seldom occur due to this movement of radios. However, if the weakening of the signal is due to the failure of a repeater a number of radios will attempt to register on an adjacent repeater site resulting in channel collision on the new site. This collision results in no radio being able to register and therefore greatly reducing the channel throughput. It is clear that a need exists for a radio and a method to successfully distinguish between situations when a radio moves out of the range of a repeater and when a repeater fails to operate.